Motor starters may also be referred to as “soft starters”. In a motor starter such as this, the motor is connected during a starting phase by the power semiconductor switch which, for example, is in the form of a thyristor, while the parallel bypass switch is open. In this case, the starting power for the motor is continuously and gradually increased, in particular in a regulated form, by appropriately driving the power semiconductor switch, such that the motor starts “softly” rather than suddenly.
During operation of the motor, the power semiconductor switches that are normally used would, however, disadvantageously result in a comparatively high power loss. In order to avoid this power loss, once the starting phase has been completed, the supply current for the motor is no longer passed via the power semiconductor switch but via the bypass switch, whose losses are considerably less, because it is a mechanical switching element.
A conventional electromechanical switching unit is normally used as the bypass switch and generally has a magnetic operating unit in order to operate the actual mechanical switching element. The bypass switch is driven by control electronics which are accommodated in the so-called printed circuit board assembly. The printed circuit board assembly is normally mounted above or alongside the bypass switch and makes contact with the bypass switch by way of essentially free wire lines. The lines are, for example, soldered by appropriate connections to the printed circuit board assembly, and make contact with the bypass switch by way of a plug connection.
This conventional solution is on the one hand comparatively space-consuming, in particular because sufficient free space must be provided for the lines in the enclosure of the motor starter. The contact between the printed circuit board assembly and the bypass switch furthermore involves a comparatively high degree of installation and material complexity. Furthermore, the lines which are essentially loose in the installed state and therefore to a certain extent hang in the appliance in an uncontrolled manner result in a certain risk of interference, in terms of electromagnetic compatibility (EMV) and likewise a certain risk of malfunction as a result of incorrectly connected lines or an incorrect plug contact.